Abstract
The surface electronic states of 15 kinds of real metals have been investigated by temperature programmed photoelectron emission (TPPE) and XPS. The characteristics of the TPPE method are the amount of emitted photoelectrons (PE total count) and the photoelectric threshold value measured at different temperatures in the temperature-increase and subsequent temperature-decrease process. The metal surfaces were pretreated using ultrasonic cleaning in acetone (T1) and exposure to argon plasma (T2). The characteristics depended strongly on the metals and the pretreatments. The PE total count and threshold value for T1 and T2 were compared: for the PE total count the metals with the order T1>T2 were Pt, Cu, Ag, Au, Ta, Nb, and Co, those with almost the same level (T1≈T2) were Al, Pb, W, Ti, and Mo, and those with the order T1<T2 were Ni, Fe, and Sn; for the threshold value the metal with the order T1>T2 was Sn, those with almost the same level (T1≈T2) were Al, Pb, Au, Ni, Ta, W, Mo, Nb, Co, and Fe, those with the order T1<T2 were Pt, Cu, Ag, and Ti. The relationship between the PE total count and the threshold value obtained for both T1 and T2 pretreatments was investigated. The metals whose PE total count tended to decrease with increasing threshold value were Pt, Cu, Ag, Au, Ni, Zn, and Sn. The metals whose threshold values varied little in spite of the variation of the PE total count were Al, Pb, Ta, Pd, W, Ti, Mo, Nb, Co, and Fe. The TPPE method was demonstrated to be able to analyze very sensitively the dependence of the electronic state of real metal surfaces on the pretreatments.
